1. Field of the Invention
The present invention relates to an apparatus for separating piled iron sheets one by one, and more particularly to a separating apparatus using a magnetic force.
2. Description of the Prior Art
A sheet feeder adapted to remove piled iron sheets (blanks) one by one from an accommodating section (stocker) and to feed them to a press machine is provided for a press machine, for example. This sheet feeder is constituted by the aforementioned separating apparatus which separates piled iron sheets one by one and a conveyor for conveying the iron sheets separated from the separating apparatus. As a separating apparatus, one which uses a magnetic force (e.g. Japanese Patent Laid-Open No. 165847/1984) tends to be used widely since its structure is simple.
FIG. 8 shows a conventional separating apparatus which makes use of such a magnetic force. A separating apparatus which is denoted by reference numeral 1 contains in a rectangular parallelepiped-shape case 2 a permanent magnet 3 in such a manner that the north and south poles (N and S poles) are arranged horizontally. If this separating apparatus 1 is brought into contact with piled iron sheets 4a, 4b, ..., a flow of a large magnetic flux is generated in end portions of the iron sheets 4a, 4b, i.e., portions in the vicinity of the contacting portions, as shown by an arrow A with a dotted line, so that the N pole and the S pole are led to portions of the iron sheets corresponding to the N pole and the S pole of the magnet 3, respectively. Consequently, reactionary forces are generated at a position between the adjacent iron sheets 4a, 4b, ... owing to the same polarity, and the iron sheets 4a, 4b, ... are separated from each other, as shown in the drawing. Incidentally, the separated iron sheets are removed consecutively as each of them is lifted up by a vacuum cup or a magnet plate (neither are shown).
However, with the above-described separating apparatus, as shown in FIG. 9, horizontal sucking forces Fp' acting toward the side of the separating apparatus 1 act on the iron sheets 4a, 4b, ... in addition to vertically separating forces Fs'. In addition, this suction force Fp' is generally greater than the separating force Fs'. For this reason, at the time when the uppermost iron sheet 4a is lifted up, a large frictional force acts between the case 2 of the separating apparatus 1 and the iron sheet. Consequently, there have been cases where the iron sheet 4a drops from the vacuum cup or the magnetic plate.
In addition, the separating force Fs' is very small unless the iron sheets 4a, 4b, ... abut uniformly against the case 2 of the separating apparatus 1. Accordingly, a special guide for positioning and guiding the iron sheets into the stocker has been required. In addition, the external configuration of the separating apparatus has been restricted to a square type, so that the separation of iron sheets having a different configuration has been impossible. Thus, there have been drawbacks in that numerous restrictions are imposed in practical use.